1. Field of the Invention
The present invention relates to an organic electroluminescent device. More particularly, the present invention relates to an organic electroluminescent (EL) device having a polarizer for realizing “real black” darkness.
2. Description of the Related Art
In order for grayscale to be adjusted on a per pixel basis, transmitted light is modulated according to an input image signal in a liquid crystal display device, and pixels directly radiate light at a luminance level indicated by an input image signal in an organic electroluminescent (EL) device. A layer modulating transmitted light or luminance level for each pixel is referred to as a modulation layer. The liquid crystal layer of a liquid crystal display device and the emission layer of an organic electroluminescent device correspond to the modulation layer.
As the liquid crystal layer is not a light valve completely blocking light, a liquid crystal display device employs two polarizing plates at two sides of the liquid crystal layer (one for the backlight and another for the display screen). To compensate for light loss caused by such polarizing plates, the contrast ratio of such a liquid crystal display device should be boosted.
The emission layer of an organic electroluminescent device does not radiate light when voltage is not applied thereto. Hence, the organic electroluminescent device may realize real black darkness and provide a higher contrast ratio in comparison to a liquid crystal display device. Organic electroluminescent devices do not require a polarizing plate related to the display screen to block light emission during black color display. However, when the organic electroluminescent device is utilized in outdoor activities, the internal metal wiring may reflect light incident from the outside and the contrast ratio may be lowered accordingly. The internal metal wiring may reflect incident light (unrelated to screen display) even during black color display, causing contrast degradation. Accordingly, to prevent contrast degradation due to reflection, the organic electroluminescent device may employ a polarizing member (a combination of a polarizing plate and wave plate) for the display screen.
However, as such configuration includes an air layer having a distinct refractive index between the topmost glass substrate and the polarizing member, the polarizing member may also reflect light incident from the outside of the glass substrate to the inside thereof. A method is desired that not only minimizes reflection of light incident from the outside but also enhances transmittance of self-emissive light.